On April 7, St. Louis County, Missouri, held a special election for County Commission, 6th district. The vote was: Democrat Kevin O’Leary 53.9%; Republican Tony Pousosa 42.3%; Constitution Party nominee Cynthia Redburn 3.8%. See this story. Redburn would not have been on the ballot but for the fact that the Constitution Party filed a federal lawsuit against the county ordinance that said in special elections, only the nominees of the two parties that polled first and second for Governor could be on the ballot.
http://www.mofreedom.org/2015/02/constitution-party-on-special-election-ballot/